Transmission fluid in vehicles with automatic transmissions, is circulated through a filter to remove particles that may damage mechanical components of the transmission. These particles may include metal particles that can be particularly damaging to the transmission components.
A prior art transmission fluid filter 10, such as the transmission filter disclosed in U.S. Pat. No. 6,139,737 (Gizowski), includes such a conventional bypass valve 11 in housing 23 (see FIG. 1). The bypass valve 11 includes a tubular valve body 12 attached to, and axially extending from the distal end of post 13. The valve 11 further includes a plunger 14 which is slidably received in the valve body 12, and plunger spring 15 is received in valve body 12 between post 13 and plunger 14. Retainer 16 (which is integrally molded with the upper body 17), is positioned between bypass valve 11 and inlet end wall 18, and retainer spring 19 attaches retainer 16 to end wall 18. If filter media 20 becomes plugged during use of filter 10, the differential pressure between inlet 21 and outlet 22 overcomes the bias of the plunger spring 15, shifting plunger 14 toward post 13. This allows fluid to pass through valve body 12 into post 13, thereby bypassing filter media 20. Thus, although the fluid is not filtered, it does not clog the filter 20 and result in overheating of the transmission.
However, Gizowski and other conventional transmission filters suffer from the disadvantage that, since the inlet end 21 and outlet end 22 are similar in appearance, if the filter 10 is placed in the transmission of the vehicle backwards (i.e., fluid entering through outlet 22 and exiting through inlet 21), then a clog occurs, which restricts the flow of transmission fluid through the filter 10 resulting in the vehicle transmission overheating and causing damage to the vehicle transmission.